Piezo bridge installation on electric guitar

[jamie884]

I need some help on this wiring. I’m putting piezo saddles in my PRS SE custom 24 (this is being done on a budget before spending lots of money on a Fishman or graphtech system). The piezo saddles have individual wires each and are going to connect to an ‘analogue workshop’ preamp. I want the tone control to have the same coil split as stock and I want a volume push pull to turn on and off the piezo/mag (I don’t need to blend the mag/piezo) these will run to a stereo jack so I can have a Y cable that splits to 2 different lines going into my line 6 helix.

My issue is I don’t actually know how to wire this all up, any help would be great!

[newey]

jamie884-

Hello and Welcome to G-Nutz2!

The piezo saddles have individual wires each and are going to connect to an ‘analogue workshop’ preamp.

I am going to assume that you have some sort of a wiring diagram for the piezo saddles and the preamp wiring, battery, etc. If not, we're going to need to know more information about the piezo preamp. Assuming you have a diagram for that already, we can just deal with the + and - connections from the preamp and treat the whole piezo system as a "black box" with 2 wires coming out of it to connect to the push/pull. If so, both our lives will be considerably easier . . .

I want the tone control to have the same coil split as stock

A diagram of the stock PRS wiring would be helpful here, so we don't have to go do a web search to see how the guitar is wired now. however, if the guitar is wired as stock now, with a push/pull on the tone pot to split a coil (or coils), you shouldn't need to redo any of the stock wiring except for the connections to the output jack- the changes will all be "downstream" of the mag pickup pts, switching, etc.

these will run to a stereo jack so I can have a Y cable that splits to 2 different lines going into my line 6 helix.

Typically, in a guitar with an active preamp like you will have, a stereo jack (Called a "TRS jack", for "Tip-ring-sleeve") is used to disconnect the battery when the guitar is unplugged, so that the battery doesn't drain when you're not using it. Here, if you are going to use a TRS jack to connect the piezo and mag pickups to a Y-split cable, you can't use the ring connection to disconnect the battery. You can certainly do it the way you propose, but you may find yourself changing batteries more frequently. However, there are also TRRS jacks, with 2 ring connections. One of those would allow you to both have the stereo output and disconnect the battery as well.

Since you won't be mixing the piezo and mag signals, you may also want to consider scratching the push/pull pot to switch between piezo and mag, and make up a "Y" stompbox to do the switching. In a gig situation, it's quicker and easier to use a footswitch to swap the outputs and it simplifies the wiring inside the guitar by eliminating the push/pull switch. A stompbox enclosure, extra jacks, and footswitches aren't terribly expense, and if you have an old stompbox that you no longer use, you can cannibalize that for the parts you'll need. Just a suggestion.

As far as your original plan, and again, ignoring the preamp wiring, you would wire one pole of the push/pull to switch the piezo on or off the jack connection, and the other pole to disconnect the mag pickups. Pretty straightforward, I'll do a diagram in a bit for you.

[newey]

OK, I worked up a basic diagram but I have some questions. First, I'm not sure if you can avoid switching the ground connections for the mag and piezo outputs, my diagram would assume they both get wired to a common ground point (back of a pot, usually) which then connects to the jack sleeve. But with an active preamp, you may need to disconnect both + and - connections for both piezo and mag pickups. If so, a push/pull won't do the trick, we'd have to come up with a different switching idea. So let's get someone else to weigh in on that as I am unsure.

Also note that the diagram just shows the wiring to the switch portion of the push/pull, the wiring to the volume pot itself won't change from the way it is wired by PRS. Also note that with this scheme, you won't have V and T controls for the piezo pickups, only for the magnetics. You'd have to control the piezo output and tone at the amp end of things. While it would be possible to wire the V push/pull to switch the V and T pots from piezo to mag, an active circuit like your piezo setup will need very different pot values from the stock pots (which in a HH guitar are likely 500KΩ) Dual gang pots for both V and T controls could solve that issue but I don't know that a dual-gang pot exists with the 2 different values you would need- the piezo preamp will likely want to "see" something like a 25K or 59KΩ pot.

If you went with a stompbox as I mentioned above, you could put separate V and T pots for the piezo in there as well, save you from controlling it at the amp.

Anyway, here's my take but as I said, let's see what others think.

[jamie884]

Thank you for the quick response! So here’s a link to the Prs diagram

support.prsguitars.com/hc/en-us/article_attachments/26568240441243

I don’t currently have a diagram for the pre amp but I’m trying to get it before it arrives. It does however, have an ‘in, ground, +9v, ground and an out’ if that helps?

With regards to the jack input maybe the TRRS would be better, can you recommend one?

For the ABY stomp, I’m pretty sure my helix is capable of doing this so would the Y cable still go into channel 1 and 2 then use the ABY to switch signals?

Also thank you for your diagram, when coming up with the idea I got in touch with Fishman and they said you can short the circuit to ground (usually the back of the pot).

Let me know your thoughts!

Many thanks

[newey]

Nov 9, 2024 15:34:51 GMT -5 jamie884 said:

For the ABY stomp, I’m pretty sure my helix is capable of doing this so would the Y cable still go into channel 1 and 2 then use the ABY to switch signals?

That's the way I was envisioning it, yes. Or to two separate amps. I have seen rigs where the piezo goes through an acoustic amp for a clean sound and the mag pickups get routed through the pedal board and to a high-gain guitar amp. Preset each amp for the tone you want and toggle between the two with the ABY switch. BTW, I built me an ABY pedal from a kit, came with the enclosure and everything, I think it cost me about 25 bucks or so (but this was a number of years ago. Took all of about 15 minutes of soldering to put it together.

I have to hit the matress here, so no time to google search for the jack. It needs to be a 1/4 inch size, obviously. Digi-Key or Mouser are your go-to for this sort of thing. Guitar parts places usually don't carry them, they're not as Nutz™ as we are.